This invention pertains to a control system for a two cycle internal combustion engine adapted to control a rotational direction of the engine in a reverse direction.
There have been used many two cycle gasoline engine (referred to as a two cycle internal combustion engine later) which can easily start by wire-recoiling, kicking or the like and can be provided in an small-sized and inexpensive manner as a primer for a traveling machine such as a scooter or a snowmobile which is required to be easily operated.
Since such a traveling machine comprises a transmission having no backup gear provided therein, the entire machine has been brought up and turned so that a front side thereof is directed in a back side in order to reverse a travelling direction thereof when it should be reversed in a narrow place etc., which causes the traveling machine to have a poor operation ability.
Of late, it has been considered that the traveling machine is adapted to have a backward traveling function by switching the two cycle internal combustion engine from the forward direction to the reverse direction in view of the characteristic of the two cycle internal combustion engine being able to normally operated in either of the forward and reverse directions.
It is required for driving the traveling machine in a forward or backward direction to arbitrarily switch the rotational direction of the two cycle internal combustion engine in accordance with a driver""s instruction.
Such control devices as control to switch the rotational direction of the internal combustion engine are disclosed in U.S. Pat. No. 3,036,802, JP11-93719, JP11-82270 and JP9-252378.
These control devices serve to fully lower the revolution of the internal combustion engine for restraining the inertia of the engine as much as possible when the reversion instruction is provided by the driver. When the revolution of the engine is fully lowered, the ignition of the engine is made at an overadvanced position (a position where the ignition position is further more advanced than the most advanced position suitable for the usual operation) whereby a piston of the engine is forced back so as to rotate the internal combustion engine in a reverse direction. When it is confirmed that the engine is rotated in the reverse direction, the engine is ignited at the ignition position suitable for maintaining the rotation of the engine in the reverse direction so that the engine is operated while the rotational direction of the engine is kept reversed.
Various methods have been proposed which lower the revolution of the engine when the reversion instruction is provided. In these methods, the engine fails to be ignited as disclosed in U.S. Pat. No. 3,036,802, an injection of fuel from an injector which supplies the fuel into the engine is stopped as disclosed in JP11-93719, the ignition position is gradually advanced as disclosed in JP11-82270 and the ignition position is gradually delayed as disclosed in JP9-252378.
These control devices is provided with induction type signal generator means comprising a rotor having reluctors mounted on a crank shaft of the engine and a pulser (signal generator) to detect the rotor type reluctors to generate a pulse signal. The information about the revolution of the engine and the rotary angle position of the crank shaft are read from the pulses generated by the signal generator means and the ignition position of the engine and the injection time of the fuel are controlled by using the information.
The control devices to control to rotate the engine in the reverse direction are adapted to ignite the engine at a position suitable for maintaining the rotation of the engine in the reverse direction after the rotational direction of the engine in the reverse direction which is accomplished by the igniting the engine at the overadvanced position is confirmed. Thus, it will be noted that the control devices are required to comprise means to detect the rotational direction of the engine.
The proposed control devices comprise signal generator means including reluctors of particular figure to detect the rotational direction of the engine. The rotational direction of the engine is detected from the phase relation of the pulses obtained by the signal generator means after the engine is ignited at the overadvanced position and thereafter the engine is ignited at the position suitable for rotating the engine in the detected rotational direction.
Since the revolution of the engine cannot be arithmetically operated in a precise manner when the engine starts and therefore the ignition position of the engine cannot be decided by the arithmetical operation, the signal generator means is so constructed as to generate pulses of positive polarity at a position slightly advanced relative to a top dead center of respective cylinders (a position of 12xc2x0 before the top dead center, for example) when the engine rotates in the forward direction. An ignition timing signal is applied to an ignition system whenever the pulses of positive polarity are generated when the engine starts whereby the ignition of the respective cylinders are made.
When the ignition of the engine is made at the overadvanced position for reversing the rotational direction of the engine, the explosion power generated by the ignition is applied against the inertia of the engine which tries to maintain the present rotation of the engine and the engine is successfully rotated in the reverse direction when the explosion power overcomes the inertia. If the explosion power is defeated by the inertia, then the engine fails to be rotated in the reverse direction. If the explosion power is equal to the inertia, then the engine stops.
In any cases, since the engine is in the condition of being rotated by a slight difference between the explosion power and the inertia after the engine is ignited at the overadvanced position and before the rotational direction of the engine is confirmed, the engine tends to easily stop. In order to maintain the rotation of the engine in this condition, the engine desirably continues to be ignited. However, in the prior art control devices, since the engine cannot continue to be ignited during the period after the ignition of the engine is made at the overadvanced position and before the rotational direction of the engine is detected, the engine tends to be undesirably stalled during the period.
It is considered that the engine is ignited by applying to the ignition system the pulses generated by the signal generator means as the ignition timing signal during the transient period after the engine is ignited at the overadvanced position and before the rotational direction of the engine is detected. However, the pulses which can be used as the ignition timing signal when the engine rotates at low speed are only the ones of positive polarity among the pulses generated by the conventional signal generator means. Since the pulses generated by the signal generator means when the engine rotates in the reverse direction is generated at the position not suitable for any ignition position, the pulses generated by the signal generator means during the transient period after the engine is ignited at the overadvanced position and until the reversion of the engine is confirmed cannot be used as the ignition timing signal.
Accordingly, it is a principal object of the invention to provide a control system for a two cycle internal combustion engine so constructed for the engine to never fail to stall during the period after the engine is ignited at the overadvanced position for operating the engine in the reverse direction until it is confirmed that the rotational direction of the engine is reversed.
The present invention relates to a control system for a two cycle internal combustion engine comprising reversion instruction generator means to generate a reversion instruction to instruct a rotational direction of the internal combustion engine to be reversed and a control unit to control the internal combustion engine so as to accomplish a speed reduction step of reducing a revolution of the internal combustion engine when the reversion instruction is generated and an overadvanced ignition step of igniting the internal combustion engine at an overadvanced position for reversing the rotational direction of the internal combustion engine when the revolution of the internal combustion engine is reduced to an overadvance starting revolution by the speed reduction step.
In the present invention, the control system further comprises signal generator means to generate low speed ignition position detection pulses at a position suitable for a low speed ignition position in a condition where the internal combustion engine rotates in a forward direction when it rotates in the forward direction and to generate low speed ignition position detection pulses at a position suitable for a low speed ignition position in a condition where the internal combustion engine rotates in a reverse direction when it rotates in the reverse direction.
Furthermore, the control unit includes transient period ignition control means to ignite the internal combustion engine at a position where the signal generator means generates the low speed ignition position detection pulses after the overadvanced ignition step is performed.
With the control system constructed as aforementioned, the internal combustion engine can be ignited at the position suitable for the low speed ignition position even though the rotational direction of the engine succeeds or fails to be reversed in the transient condition after the engine is ignited at the overadvanced position. It will be noted that this prevents the engine from failing to stall after the engine is ignited at the overadvanced position in order to reverse the rotational direction of the engine.
In case that the internal combustion engine has n (n is an integral number of 1 or more than) cylinders, the signal generator means includes a rotor mounted on a crank shaft of the engine and having n reluctors provided so as to correspond to the respective cylinders in the engine with a thickness and a width of the reluctors uniform in a rotational direction of the crank shaft of the engine and pulsers disposed at positions where the reluctors of the rotor can be detected to generate low speed ignition position detection pulses for the respective cylinders when front edges of the reluctors corresponding to the respective cylinders as viewed in the rotational direction are detected.
The reluctors corresponds to the respective cylinders being provided so that both peripheral ends of the reluctors are positioned in both sides of a linear line bonding a center of the crank shaft and a center of a magnetic pole of the corresponding pulser when a piston of the respective cylinders of the internal combustion engine reaches the top dead center and the both peripheral ends of the reluctors are so set that the pulser generates the low speed ignition position detection pulses at a position suitable for an ignition position for the cylinders in the internal combustion engine even though the engine rotates in either of rotational directions.
The control unit includes transient period ignition control means which is so constructed as to ignite the internal combustion engine when the signal generator means detects the front edge of the reluctor corresponding to each one of the cylinders to generate the low speed ignition position detection pulses after the overadvanced ignition step is performed.
In practically making the control system, there is required to be provided means to obtain an information used for deciding the rotational direction of the internal combustion engine. In case that the engine is a multi-cylinder engine having 2 or more than cylinders, there is required to be provided means to obtain a rotary angle information used for deciding which of the cylinders should be ignited or to which of the cylinders the fuel should be injected.
In order to obtain the information on the rotational direction of the engine and on the decision of the cylinder, there may be provided signal generator means separate from the one for obtaining the signal determining the low speed ignition position, but single signal generator means may be preferably provided to obtain all the informations on the rotation of the engine, which causes the construction to be simplified.
To this end, the signal generator means preferably comprises a rotor mounted on the crank shaft of the engine and having first and second inductor magnetic pole portions provided so as to be offset from each other in an axial direction of the crank shaft of the internal combustion engine and first and second pulseres provided corresponding to the first and second inductor magnetic pole portions, respectively.
The first inductor magnetic pole portion has n first reluctors formed with a thickness and a width uniform in the rotational direction of the crank shaft and disposed at an equal angular distance corresponding to the n (n is an integral number of 2 or more than) cylinders in the engine while the second inductor magnetic pole portion has n second reluctor including one two step reluctor portion of first and second portions arranged in the rotational direction of the crank shaft and formed so that a boundary of the first and second portions changes in their thickness and width and (nxe2x88x921) one step reluctor portions formed so as to have a thickness and a width uniform in the rotational direction of the crank shaft. In this case, the second reluctors are disposed at an equal angular distance with the two step reluctor portion corresponding to one of the cylinders of the internal combustion engine and with the (nxe2x88x921) one step reluctor portions corresponding to the cylinders other than the one of the cylinders.
The first pulser is so constructed as to be disposed so as to be able to detect each of the reluctors of the first inductor magnetic pole portions of the rotor to generate pulses of different polarities when both of the peripheral ends of the reluctors of the first inductor magnetic pole portion detected. The second pulser is so constructed as to be disposed so as to be able to detect the two step reluctor and the one step reluctors of the second inductor magnetic pole portion of the rotor to generate a pair of pulses of the same polarity, respectively when the end of the two step reluctor in the side of the first portion and the boundary are detected, respectively, a single pulse of polarity different from the polarity of the pair of pulses when the end of the two step reluctor in the side of the second portion is detected and pulses of different polarities, respectively when the both ends of the one step reluctor are detected.
The first reluctors corresponding to the respective cylinders are so set that the first pulsers generate pulses at a position suitable for a low speed ignition position for the cylinder in the internal combustion engine when the first pulsers detect the front edges of the first reluctors corresponding to the respective cylinders in the rotational direction even though the engine rotates in either of rotational directions.
The control unit comprises transient period ignition control means to ignite the internal combustion engine when the front edges of the first reluctors in the rotational direction are detected after the overadvanced ignition step is performed, rotational direction detection means to detect the rotational direction of the internal combustion engine on a phase relation between the pair of pulses and the single pulse generated by the second pulser, revolution arithmetical operation means to arithmetically operate a revolution of the internal combustion engine on a generation distance of the pulses generated by the first pulser or on a generation distance of the pulses generated by the second pulser, ignition position arithmetical operation means to arithmetically operate an ignition position of the internal combustion engine at the revolution arithmetically operated by the revolution arithmetical operation means, cylinder judgment means to judge which of the cylinders should be ignited on a phase relation between the pair of pulses and the single pulse generated by the second pulser and ignition position control means to control the cylinder judged by the cylinder judgement means to be ignited at the ignition position arithmetically operated by the ignition position arithmetical operation means so as to maintain the rotation of the internal combustion engine in the rotational direction detected by the rotational direction detection means.
With the signal generator means constructed as aforementioned, the rotational direction of the engine can be judged by determining the phase relation between the pair of pulses of the same polarity generated when the second pulser detects the two step reluctor and the single pulse of polarity different from that of the pair of the pulses. Since which of the cylinders corresponds to the reluctors detected to generate the pulses can be judged by detecting the generation order of the pulses of positive and negative polarities generated by the first and second pursers, the informations on the judgment of the cylinders to be ignited and the judgment of the cylinders to which the fuel should be injected can be more easily obtained.